1. Field of the Invention
This invention relates broadly to method and apparatus for cleaning the exterior surface of a pipe ordinarily located in a sub-sea environment. In particular, the invention has regard to method and apparatus for removing concrete from a pipe precoated with same.
2. Description of the Prior Art
Ordinarily, pipelines laid in a sub-sea environment include a heavy external coating of concrete in order to maintain the pipeline in a submerged condition on sea bottom. Under certain circumstances however, the pipeline may become damaged requiring the damaged section to be cut from and replaced with a new section of pipe. To enable the damaged section to be cut from the pipeline it will be understood that the concrete must first be removed to expose the pipe for cutting purposes.
In one known concrete removal operation, a device having a nozzle is attached to the pipe whereupon the nozzle is moved longitudinally and circumferentially about the pipe to direct a high pressure stream of fluid against the pipe to disintegrate the concrete and remove it therefrom. This operation, however, has one drawback in that very large hydraulic forces are required to obtain the desired pressurized stream characteristics, particularly at great depths. Another drawback is the fact that this concrete removal operation is time consuming because the pressurized stream must contact all areas of the coating in order to disintegrate it.